Slimline CD DVD drive
The drive just fits into the upper half of the metal cover.
Either IDE or SATA will do, with corresponding USB adapter. The IDE drive with USB adapter costs approx. 12USD incl. shipping.
The drive needs a rectangular cut-out in the side of the upper cover. Make it just a bit larger to allow smooth tray movement.
The drive is placed onto two pieces of 6mm thick plates. I used wood since they are glued to the cover. The plates carry four M4 bolts.
The drive is fastened with two plates made of PCB. The holders are stiffened with 3mm high ribs. The rear plate has a rectangular cut out to make room for the analog connector on the board.
Do not let the M4 bolts extend too far so that they do not collide with the board.